[ARM] make page_to_dma() highmem aware

If a machine class has a custom __virt_to_bus() implementation then it
must provide a __arch_page_to_dma() implementation as well which is
_not_ based on page_address() to support highmem.

This patch fixes existing __arch_page_to_dma() and provide a default
implementation otherwise.  The default implementation for highmem is
based on __pfn_to_bus() which is defined only when no custom
__virt_to_bus() is provided by the machine class.

That leaves only ebsa110 and footbridge which cannot support highmem
until they provide their own __arch_page_to_dma() implementation.
But highmem support on those legacy platforms with limited memory is
certainly not a priority.

Signed-off-by: Nicolas Pitre <nico@marvell.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index 59fa762e9c66..ff46dfa68a97 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -15,10 +15,20 @@
  * must not be used by drivers.
  */
 #ifndef __arch_page_to_dma
+
+#if !defined(CONFIG_HIGHMEM)
 static inline dma_addr_t page_to_dma(struct device *dev, struct page *page)
 {
         return (dma_addr_t)__virt_to_bus((unsigned long)page_address(page));
 }
+#elif defined(__pfn_to_bus)
+static inline dma_addr_t page_to_dma(struct device *dev, struct page *page)
+{
+        return (dma_addr_t)__pfn_to_bus(page_to_pfn(page));
+}
+#else
+#error "this machine class needs to define __arch_page_to_dma to use HIGHMEM"
+#endif
 
 static inline void *dma_to_virt(struct device *dev, dma_addr_t addr)
 {
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index ae472bc376d3..85763db87449 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -188,6 +188,7 @@ static inline void *phys_to_virt(unsigned long x)
 #ifndef __virt_to_bus
 #define __virt_to_bus   __virt_to_phys
 #define __bus_to_virt   __phys_to_virt
+#define __pfn_to_bus(x) ((x) << PAGE_SHIFT)
 #endif
 
 static inline __deprecated unsigned long virt_to_bus(void *x)